Low-solvent or solvent-free light-stable two-component polyurethane lacquers are known and have been described in U.S. application Ser. No. 438,049, filed Jan. 30, 1974, now abandoned. The lacquer systems described in this patent application have considerable advantages over the prior art as it existed at the time the invention therein was made. However, the polyisocyanates with an NCO-functionality of greater than 2 which are described as being particularly suitable in the above-mentioned application have high viscosities (i.e., in the range of from about 1000 to 2500 cP at 20.degree. C.), with the result that relatively large quantities of "reactive diluents" have to be used in the lacquer systems for achieving a spraying viscosity. The cycloaliphatic diisocyanates which are also mentioned in U.S. Ser. No. 438,049 are only of limited suitability for the application in question because of their relatively low NCO-functionality and their physiological incompatibility.
Accordingly, an object of the present invention was to provide new polyisocyanates with aliphatic isocyanate groups, NCO-functionalities of greater than 2 and viscosities of less than 200 cP at 20.degree. C. In addition, the new isocyanates were preferably to contain NCO-groups attached to primary carbon atoms in order to meet practical requirements in regard to the reactivity with compounds containing isocyanate-reactive groups. Finally, the new isocyanates were to have a low vapor pressure and were to be substantially odorless at room temperature.